This study aimed to extend our theoretical understanding of how mindfulness-based interventions exert their positive influence on measures of occupational health. Employing a randomized waitlist control study design, we sought to (a) assess an Internet-based instructor-led mindfulness intervention for its effect on key factors associated with “recovery from work,” specifically, work-related rumination, fatigue, and sleep quality; (b) assess different facets of mindfulness (acting with awareness, describing, nonjudging, and nonreacting) as mechanisms of change; and (c) assess whether the effect of the intervention was maintained over time by following up our participants after 3 and 6 months. Participants who completed the mindfulness intervention (n = 60) reported significantly lower levels of work-related rumination and fatigue, and significantly higher levels of sleep quality, when compared with waitlist control participants (n = 58). Effects of the intervention were maintained at 3- and 6-month follow-up with medium to large effect sizes. The effect of the intervention was primarily explained by increased levels of only 1 facet of mindfulness (acting with awareness). This study provides support for online mindfulness interventions to aid recovery from work and furthers our understanding with regard to how mindfulness interventions exert their positive effects.